In warehouses, retail establishments, shipping centers and other places where products are stored, it is convenient to affix electronic labels on or adjacent to products to identify the product and include other important information such as price, product destination, country of origin, etc. Because the information displayed on electronic labels often needs to be changed or updated, it is particularly useful to be able to remotely control the information displayed on the electronic label.
Various electronic label systems have been proposed. For example, U.S. Pat. No. 6,715,676 describes an electronic price label in which an infrared LED array is used to transmit information to a receiver on the label. This receiver is an IR-filtered photodiode. A separate solar cell is used to charge a battery to power a label display.
U.S. Pat. No. 5,635,915 describes a product pricing system for a supermarket in which electronic shelf labels are provided with pricing information by modulating fluorescent lamps in the store. The information is received by a photodiode. A liquid crystal display is powered by a battery charged by a solar cell.
Liquid crystal displays in prior electronic labels use considerable energy to maintain the visible indication of information, resulting in the need for frequent battery replacement. Further problems with prior art electronic labels relate to complexity of delivery of information such as the need for RF or IR transmitters; some prior art labels also require considerable power consumption to send out response messages to a control system. Additionally, prior art labels typically use separate devices to receive signals and to charge batteries, resulting in additional complexity and expense.
Thus there is a need in the art for remotely-controllable electronic labels that are low in power consumption, simple in design, and use a low power and easy-to-modulate source of signals.